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Entamoeba histolytica cysts with a defective wall formed under axenic conditions
S Said-Fernández1, B D Mata-Cárdenas, M T González-Garza
1División de Biología Celular, Instituto Mexicano del Seguro Social, Monterrey, Nuevo León.
Abstract:
Axenic HK9 Entamoeba histolytica strain amoebae, maintained in PEHS medium, displayed several cystic characteristics that involve an active process of cystic wall formation, cellular volume and density diminution, and one or two nuclear divisions. The differentiation process was asynchronic, beginning after the logarithmic growth phase. The axenic cysts, which were maintained in a 50 mOsm/kg medium at 4 degrees C for 72 h, produced growing trophozoites within 1-7 days of incubation at 36 degrees C in fresh medium. Negative results were obtained with trophozoites submitted to the above treatment, and with axenic cysts maintained in double-distilled water at 4 degrees C for 24 h, or in 0.1% sarkosyl, for 10 min at room temperature instead of 55 mosmol/kg medium. Thus, the HK9 E. histolytica strain, cultured in PEHPS, produced under axenic conditions a small proportion of mature, metabolically active cysts, but with an immature or abnormal wall.
Insights
Axenic Entamoeba histolytica HK9 strain can form cysts under specific laboratory conditions. However, these cysts exhibit immature walls, impacting their full maturation and metabolic activity.
Area of Science:
- Parasitology
- Microbiology
- Cell Biology
Background:
- Entamoeba histolytica is an important human parasite.
- Cyst formation is a critical stage in the parasite's life cycle.
- Understanding axenic cystogenesis is crucial for controlling amoebiasis.
Purpose of the Study:
- To investigate the conditions for axenic cyst formation in Entamoeba histolytica HK9 strain.
- To characterize the morphological and metabolic properties of these axenically derived cysts.
Main Methods:
- Culturing Entamoeba histolytica HK9 strain axenically in PEHPS medium.
- Inducing cyst formation through specific osmotic and temperature conditions.
- Assessing cyst viability and infectivity through subsequent trophozoite development.
Main Results:
- Axenic HK9 Entamoeba histolytica amoebae showed cystic characteristics including wall formation and nuclear division.
- Cyst formation was asynchronous and initiated post-logarithmic growth phase.
- Cysts maintained at 50 mOsm/kg and 4°C for 72 hours developed into trophozoites upon incubation at 36°C, indicating metabolic activity.
- Trophozoites and cysts treated with distilled water or sarkosyl did not yield viable trophozoites.
- A small proportion of mature, metabolically active cysts were produced, but with immature or abnormal walls.
Conclusions:
- Entamoeba histolytica HK9 can produce metabolically active cysts under specific axenic conditions.
- The induced cysts possess immature or abnormal walls, suggesting limitations in achieving full maturation in vitro.
- Further research is needed to optimize axenic cyst formation and wall maturation for potential applications.